The present invention relates in general to magnetic recording and reproducing apparatus for recording and reproducing an information signal on and from a magnetic tape and in particular to a cassette loading system used in a magnetic recording and reproducing apparatus for loading and unloading a magnetic tape contained in a tape cassette on and from the apparatus.
Current magnetic recording and reproducing apparatus which records and reproduces an information signal on and from a magnetic tape such as a video tape recorder is loaded with magnetic tape in a manner such that the tape is contained in a tape cassette for ease of handling as well as for protection of the magnetic tape. In order to load the magnetic tape contained in the tape cassette into the recording and reproducing system of the video tape recorder which includes a rotary drum on which magnetic heads are carried, a cassette loading system is used for transporting the tape cassette from an eject position to a predetermined loading position defined relative to the position of the rotary drum and for wrapping the tape around the rotary drum in a predetermined manner. The loading system is used also for disengaging the magnetic tape from the rotary drum and for transporting the tape cassette back to the initial eject position for removal of the tape cassette.
There are several types of tape cassettes which are currently sold in the market. One typical example of such a tape cassette is called a "standard size" tape cassette and is used widely in home video tape recorders. The aforementioned standard size tape cassette may have a typical dimension of 188.times.104.times.25 mm, for example, and accommodates a half inch wide magnetic tape wound around a supply reel and a take up reel with such an amount that a few hours of recording time is obtained. The specification for the tape cassette as well as for the recording format on the magnetic tape is standardized in relation to the type of video tape recorder so that the magnetic tape cassettes produced by different manufacturers can be used as long as the specification matches the type of video tape recorder.
Recently, a more compact video tape recorder was developed so as to realize a portable video tape recorder combined with a television camera and the like. Such a compact video tape recorder naturally uses a compact size tape cassette having a reduced size so as to decrease the size and weight of the video tape recorder. In order to reduce the size, the compact size tape cassette contains a smaller amount of magnetic tape having a substantially reduced separation between a supply reel and a take up reel. On the other hand, the recording format of the video signal and the audio signal on the tape are identical to the "standard size" tape cassette, so that the compatibility with the home video tape recorder currently in use is maintained.
Conventionally, such a compact size tape cassette is reproduced by the home video tape recorder by using an adapter having a size identical to the size of the standard size tape cassette into which the compact size tape cassette is accommodated, as the size and construction of the tape cassette do not match with the loading system of the video tape recorder designed for the standard size tape cassette. However, the use of such adapter is cumbersome and indeed inconvenient. Thus, there is a demand for a cassette loading system of a video tape recorder which can handle both the standard size tape cassette and compact size tape cassette.
According to the Laid-open Japanese Patent Application 269257/1986, a loading system of a video tape recorder is disclosed in which the size of a holder for holding the tape cassette can be changed responsive to the size of the tape cassette so that the loading system can handle the tape cassettes having different sizes. Further, there is a known loading system in which the compact size tape cassette is loaded into the video tape recorder by guiding the tape cassette along a side wall of a holder. In both of these loading systems, the tape cassette is loaded into the video tape recorder through an aperture at a front panel of the video tape recorder. As the video tape recorder has the rotary drum carrying magnetic heads at a position relatively far from the front panel, the tape cassette is usually inserted with an orientation such that a first side of the tape cassette, along which the magnetic tape is scanned by the magnetic heads, faces the rotary drum at the inside of the video tape recorder while a second side of the cassette opposite to the first side faces the outside of the video tape recorder. This means that one has to insert the compact size tape cassette relatively deeply in the video tape recorder so that the magnetic tape along the first side of the tape cassette reaches a predetermined position close to the rotary drum. However, such an operation is difficult for an ordinary person as one has to push the second side or back of the tape cassette by inserting ones finger deeply into the apparatus through the aperture at the front panel. Thus, such an operation tends to cause improper loading of the tape cassette. Further, such a loading system is complex in structure. Thus, the prior art loading system is unsatisfactory with respect to the handling of the compact size tape cassettes and an improved loading system which eliminates these problems is desired.
On the other hand, the Laid-open Japanese Patent Application 182660/1986 discloses a cassette loading system using a cassette tray on which is placed a tape cassette at the time of loading. As described previously, the tape cassette must be loaded in a proper orientation. In order to prevent erroneous loading, this prior art loading system uses projections at predetermined positions on the cassette tray which abuts with a bottom of the tape cassette when the tape cassette is loaded in an improper state. In this state, the tape cassette is held in a slightly lifted state in the loading system so that the user can inspect visually the improper loading of the tape cassette. When the tape cassette is loaded properly, on the other hand, the projection engages with a depression formed at the bottom of the tape cassette and the tape cassette is held properly in the loading system.
However, such a loading system relies upon judgement for the loading state of the tape cassette by the user who inspects the loading state only visually. Thus, there is a substantial risk that the user starts operation of the video tape recorder which is not properly loaded with the tape cassette without noticing the improper loading state of the cassette. Once the video tape recorder is started in such a state, the loading system starts to transport the tape cassette even if it is not loaded properly, and the tape cassette can be damaged seriously.
Accordingly, there is a need for a loading system of a magnetic recording and reproducing apparatus in which improper loading of the tape cassette on the loading system is detected and the loading operation of the improperly loaded cassette which may cause damage to the cassette as well as to the loading system is positively prevented.
Tape cassette according to the standardized specification generally has a front lid along the first side of the cassette such that the lid is opened to allow the magnetic tape to be drawn out at the time of recording and reproducing but is closed for protection of the magnetic tape when the cassette is not used. The front lid is locked when the lid is in the closed state by a locking member. In order to unlock the front lid, the loading system of the video tape recorder has an operating member which urges the locking member such that the lock of the lid is released when the tape cassette is properly loaded. This operating member of the loading system continuously urges the locking member as long as the tape cassette is loaded in the video tape recorder. When the tape cassette is to be removed from the video tape recorder, the urging force exerted on the locking member by the operating member is removed and the locking member is returned to an unurged state when the lid is closed. Thus, the lid is locked again in the closed state.
The return of the locking member to the unurged state is made possible by the resiliency of the locking member. In the standard size tape cassette, this resiliency of the locking member is obtained by a coil spring and the like. In the case of the compact size tape cassette, on the other hand, this resiliency of the locking member is obtained by providing resiliency to the locking member itself. For this purpose, the locking member of the compact tape cassette is made of a thin plastic material.
In such a compact size tape cassette, there is a problem that the locking member tends to become permanently deformed when the tape cassette is kept in the loaded state in the video tape recorder for a prolonged time period. Such a permanent deformation is caused as a result of the continuous action of the operating member applied to the locking member for a prolonged time period. Once the permanent deformation appears, the locking member cannot hold the front lid properly and dust and other exotic materials easily enter the tape cassette and the magnetic tape in the cassette is damaged. Thus, an improved mechanism for manipulating the locking member of the front lid of the tape cassette is needed.